Retinoid-related orphan receptors (RORs) are transcription factors which belong to the steroid hormone nuclear receptor super family. The ROR family consists of three members, ROR alpha (RORα), ROR beta (RORβ) and ROR gamma (RORγ), also known as NR1F1, NR1F2 and NR1F3 respectively (and each encoded by a separate gene RORA, RORB and RORC, respectively). RORs contain four principal domains shared by the majority of nuclear receptors: an N-terminal A/B domain, a DNA-binding domain, a hinge domain, and a ligand binding domain. Each ROR gene generates several isoforms which differ only in their N-terminal A/B domain. Two isoforms of RORγ, RORγ1 and RORγt (also known as RORγ2) have been identified.
RORγt is a truncated form of RORγ, lacking the first N-terminal 21 amino acids and is exclusively expressed in cells of the lymphoid lineage and embryonic lymphoid tissue inducers (Sun et al., Science, 2000, 288, 2369-2372; Eberl et al., Nat Immunol., 2004, 5: 64-73) in contrast to RORγ which is expressed in multiple tissues (heart, brain, kidney, lung, liver and muscle).
RORγt has been identified as a key regulator of Th17 cell differentiation. Th17 cells are a subset of T helper cells which produce IL-17 and other proinflammatory cytokines and have been shown to have key functions in several mouse autoimmune disease models including experimental autoimmune encephalomyelitis (EAE) and collagen-induced arthritis (CIA). In addition, Th17 cells have also been associated in the pathology of a variety of human inflammatory and autoimmune disorders including multiple sclerosis, rheumatoid arthritis, psoriasis, Crohn's disease and asthma (Jetten et al., Nucl. Recept. Signal, 2009, 7:e003; Manel et al., Nat. Immunol., 2008, 9, 641-649). The pathogenesis of chronic autoimmune diseases including multiple sclerosis and rheumatoid arthritis arises from the break in tolerance towards self-antigens and the development of auto-aggressive effector T cells infiltrating the target tissues. Studies have shown that Th17 cells are one of the important drivers of the inflammatory process in tissue-specific autoimmunity (Steinman et al., J. Exp. Med., 2008, 205: 1517-1522; Leung et al., Cell. Mol. Immunol., 2010 7: 182-189). Th17 cells are activated during the disease process and are responsible for recruiting other inflammatory cells types, especially neutrophils, to mediate pathology in the target tissues (Korn et al., Annu. Rev. Immunol., 2009, 27:485-517) and RORγt has been shown to play a critical role in the pathogenic responses of Th17 cells (Ivanov et al., Cell, 2006 126: 1121-1133). RORγt deficient mice have shown no Th17 cells and also resulted in amelioration of EAE. The genetic disruption of RORγ in a mouse colitis model also prevented colitis development (Buonocore et al., Nature, 2010, 464: 1371-1375). The role of RORγt in the pathogenesis of autoimmune or inflammatory diseases has been well documented in the literature. (Jetten et al., Adv. Dev. Biol., 2006, 16:313-355; Meier et al. Immunity, 2007, 26:643-654; Aloisi et al., Nat. Rev. Immunol., 2006, 6:205-217; Jager et al., J. Immunol., 2009, 183:7169-7177; Serafmi et al., Brain Pathol., 2004, 14: 164-174; Magliozzi et al., Brain, 2007, 130: 1089-1104; Barnes et al., Nat. Rev. Immunol., 2008, 8: 183-192).
In addition, RORγt is also shown to play a crucial role in other non-Th17 cells, such as mast cells (Hueber et al., J Immunol., 2010, 184: 3336-3340). RORγt expression and secretion of Th17-type of cytokines has also been reported in NK T-cells (Eberl et al., Nat. Immunol., 2004, 5: 64-73) and gamma-delta T-cells (Sutton et al, Nat. Immunol., 2009, 31: 331-341; Louten et al., J Allergy Clin. Immunol., 2009, 123: 1004-1011), suggesting an important function for RORγt in these cells.
PCT Publication Nos. WO 2012/139775, WO 2012/027965, WO 2012/028100, WO 2012/100732, WO 2012/100734, WO2012/064744 and WO 2013/171729 disclose heterocyclic compounds which are modulators of retinoid-related orphan receptor gamma (RORγ) receptor activity.
In view of the above, a need exists for new therapeutic agents that modulate the activity of RORγt and thus will provide new methods for treating diseases or condition associated with the modulation of RORγt.
The present application is directed to compounds that are modulators of the RORγt receptor.